fix(test): refresh authentication token off main thread

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Summary

• refresh TestAuthenticationActivity credentials on Dispatchers.IO
• keep account setup, user switching, and activity launch on the lifecycle main scope
• prevent NetworkOnMainThreadException before test apps can launch

Root cause

TestAuthenticationActivity calls AccMgrAuthTokenProvider.newAuthToken from onCreate. ClientManager now performs the refresh directly, so Firebase Test Lab aborted authentication on the main thread before the React Native HeadlessTestApp mounted.

Testing

• ./gradlew :libs:SalesforceSDK:compileDebugKotlin --no-daemon
• SalesforceMobileSDK-ReactNative headless Android suite: 35/35 JavaScript tests passed
• ReactHarnessTest.testAsyncPassing: passed

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All failing Unit Tests and most failing UI Test are caused by DPoP changes.